The world, and particularly the medical world, is primarily one of probabilities. For example, a patient contemplating a heart transplant cannot be told whether or not he will survive, but only the statistical probability that he will survive. Similarly, a patient considering taking a medication, cannot be told that the medication is effective, but only that it is, for example, 80% effective or 20% effective. This uncertainty is particularly disconcerting in diagnostic testing.
For example, expectant mothers are often tested for the level of alphafetoprotein in their blood. If the level of the protein is high, it is likely that the fetus has a neural tube defect. If the level of the protein is low, it is likely that the fetus has Down Syndrome. The test, however, is not certain. Again, the level of the protein is used only to indicate the statistical probability or risk that the fetus has one of the above mentioned conditions.
Currently, statistical probabilities regarding risk are not always conveyed to the patient clearly. Many health care professionals use threshold probabilities upon which they base their advice. If a risk exceeds a chosen threshold, they make a recommendation, e.g., a remedy to reduce or eliminate the risk or a test to more accurately determine the risk. If the risk is below the threshold then the recommendation, e.g., remedy or test, is not made. The use of a threshold value alone, however, provides no indication of how the risk increases or decreases above or below that threshold. Thus, the use of a threshold-based recommendation provides little information for the patient to independently determine whether to undergo a recommended remedy or test.
As an illustration, if the level of alphafetoprotein in the blood of an expectant mother is below a threshold level, a physician may recommend that an amniocentesis be performed to determine whether, in fact, the fetus has Down Syndrome. If the level is above the threshold level, an amniocentesis is not recommended. What is not told to the patient is whether the risk changes substantially above or below that threshold level. Depending on that change, and on the patient's aversion to amniocentesis or concern over Down Syndrome, an expectant mother whose level of alphafetoprotein is above the threshold level may still decide to accept the risks associated with amniocentesis and undergo that procedure. Likewise, an expectant mother whose alphafetoprotein level is below the threshold may nevertheless decide not to undergo the recommended amniocentesis procedure.
Accordingly, there is a need for a means to clearly indicate to the patient the results of a particular test and the risk associated with that test result together with information indicating whether the result is a normal one and how the risk changes as the result changes. The patient can then make an informed decision on how to proceed. He can use the knowledge of the risk together with his own concern regarding the remedy or further testing to make the decision which is best for him.
The invention is a method of displaying the results of testing maternal blood serum of a patient for alphafetoprotein level. Specifically, a distribution curve of alphafetoprotein levels in maternal blood serum for a population of patients is represented on a surface in cartesian coordinates, such that the distribution curve represents the number of expectant mothers on the vertical axis and the alphafetoprotein level on the horizontal axis. A gradually changing risk, increasing for Down Syndrome and decreasing for Open Spina Bifida, with decreasing alphafetoprotein levels is represented on the surface along the horizontal axis. A mark representing the alphafetoprotein level of the patient being tested is placed on the surface. The risk of Down Syndrome and/or Open Spina Bifida to the patient is displayed at the mark by the representation of risk along the horizontal axis. As a result, the patient is more easily able to assess the risk of abnormality than by prior AFP reporting techniques.